Verification of cardiac arrhythmia prior to therapeutic stimulation

Abstract

Ambulatory medical devices may occasionally improperly administer a therapeutic stimulation pulse to a patient upon an incorrect detection of arrhythmia in the patient. To address these improperly administered therapeutic stimulation pulses, an ambulatory medical device includes processes and systems for verifying an initial declaration of an arrhythmia. The ambulatory medical device described include at least one first sensing electrode and at least one second sensing electrode distinct from the at least one first sensing electrode. First electrocardiogram (ECG) signals detected by the first sensing electrode are analyzed to provide an initial declaration of the arrhythmia condition of the patient. As a treatment protocol is being initiated in response to the analysis of the first ECG signals, second ECG signals detected by the second sensing electrode are analyzed to verify the initial declaration of the arrhythmia.

1 - 22 . (canceled) 
     
     
         23 . An ambulatory medical device comprising:
 a pair of therapy electrodes configured to couple externally to a skin of a patient and to provide at least one therapeutic stimulation pulse to a heart of the patient;   a pair of sensing electrodes configured to couple externally to the skin of the patient and to acquire first and second of electrocardiogram (ECG) signals from the patient;   ECG sensing electrode circuitry coupled to the pair of sensing electrodes and configured to process the acquired first and second ECG signals from the patient to generate first and second ECG data; and   at least one processor coupled to the pair of sensing electrodes, the ECG sensing electrode circuitry, and the pair of therapy electrodes and configured to
 receive the first ECG data; 
 analyze the first ECG data using a first process to detect an arrhythmia condition of the patient; 
 record an initial declaration of the arrhythmia condition of the patient in response to detecting the arrhythmia condition; 
 initiate a treatment protocol in response to the initial declaration of the arrhythmia condition, the treatment protocol specifying provision of at least one alarm indicating an imminent delivery of the at least one therapeutic stimulation pulse and provision of the at least one therapeutic stimulation pulse; 
 cause the ECG sensing electrode circuitry to activate a second process distinct from the first process to analyze the second ECG signals; 
 receive the second ECG data; and 
 analyze, after the provision of the at least one alarm and before the provision of the at least one therapeutic stimulation pulse, the second ECG data using the second process distinct from the first process to verify the initial declaration of the arrhythmia condition. 
   
     
     
         24 . The ambulatory medical device of  claim 23 , wherein the second process is configured to have improved reliability in analyzing the second ECG signals to verify the initial declaration of the arrhythmia condition. 
     
     
         25 . The ambulatory medical device of  claim 23 , wherein the at least one processor is further configured to control delivery of the at least one therapeutic stimulation pulse in response to verifying the initial declaration of the arrhythmia condition. 
     
     
         26 . The ambulatory medical device of  claim 23 , wherein the at least one processor is further configured to:
 refute, using the second ECG data, the initial declaration of the arrhythmia condition; and   delay the provision of the at least one therapeutic stimulation pulse in response to refuting the initial declaration of the arrhythmia condition.   
     
     
         27 . The ambulatory medical device of  claim 26 , wherein the delay comprises a delay having a duration between 30 seconds and 45 seconds. 
     
     
         28 . The ambulatory medical device of  claim 23 , wherein the at least one processor is configured to analyze the second ECG data using the second process at least in part by determining a value that indicates a confidence that the second ECG data reflects normal cardiac function of the patient and evaluate the value. 
     
     
         29 . The ambulatory medical device of  claim 28 , wherein the at least one processor is configured to evaluate the value at least in part by comparing the value to a threshold value. 
     
     
         30 . The ambulatory medical device of  claim 23 , wherein the first process comprises an abnormality detection process and the second process comprises an arrhythmia verification process. 
     
     
         31 . The ambulatory medical device of  claim 30 , wherein the abnormality detection process comprises a first number of sub-processes and the arrhythmia verification process comprises a second number of sub-processes less than the first number of sub-processes. 
     
     
         32 . The ambulatory medical device of  claim 30 , wherein the abnormality detection process comprises a first set of sub-processes and the arrhythmia verification process comprises a second set of sub-processes different than the first set of sub-processes. 
     
     
         33 . The ambulatory medical device of  claim 30 , wherein the arrhythmia verification process comprises at least one of a heart rate detection sub-process or a signal morphology detection sub-process. 
     
     
         34 . The ambulatory medical device of  claim 33 , wherein the abnormality detection process comprises a first fast Fourier transform and the arrhythmia verification process omits a second fast Fourier transform. 
     
     
         35 . The ambulatory medical device of  claim 23 , wherein the at least one processor is configured to cause the ECG sensing electrode circuitry to activate the second process to analyze the second ECG signals within a predefined period of time after the initial declaration of the arrhythmia condition. 
     
     
         36 . The ambulatory medical device of  claim 35 , wherein the predefined period of time comprises a range from between 1 second to 60 seconds. 
     
     
         37 . The ambulatory medical device of  claim 35 , wherein the predefined period of time varies based on the arrhythmia condition. 
     
     
         38 . The ambulatory medical device of  claim 35 , wherein the arrhythmia condition is ventricular tachycardia and the predefined period of time comprises a range from between 8 seconds to 10 seconds. 
     
     
         39 . The ambulatory medical device of  claim 35 , wherein the arrhythmia condition is ventricular fibrillation and the predefined period of time comprises a range from between 5 seconds to 8 seconds. 
     
     
         40 . The ambulatory medical device of  claim 30 , further comprising at least one non-ECG sensor, the at least one non-ECG sensor comprising one or more of an accelerometer or a photoplethysmograph sensor, wherein the at least one processor is further coupled to the at least one non-ECG sensor and is further configured to:
 receive non-ECG data generated from signals acquired by the at least one non-ECG sensor; and   analyze the non-ECG data with the abnormality detection process to contribute to detection of the arrhythmia condition.   
     
     
         41 . The ambulatory medical device of  claim 23 , further comprising a garment housing the pair of sensing electrodes, wherein the second process comprises a process to tighten the garment around the patient.